374
S. Mitra et al.
application in a variety of different branches such as lithium-ion batteries (Wu et al.
2010), supercapacitors (Bose et al. 2017a, b), electronic devices (Guo et al. 2010),
tribology (Eswaraiah et al. 2011), and fillers for nanocomposites (Bose et al. 2017a,
b, 2018, 2019). Therefore, huge requisition for graphene and its peaking cost of largescale production demands substantial reduction in the production cost associated with
it. Compared to the preparation of graphene from graphite using various mechanical
routes (Dikin et al. 2007), the reduction of graphene oxide (GO) offers a promising
alternative for the mass production of graphene. Properties of the reduced graphene
oxide (RGO) are affected by the characteristics of the GO used in the synthesis step
(Subrahmanyam et al. 2009). The reduction of GO via electrochemical (Raj and John
2013), thermal (Liu et al. 2013), and photocatalytic (Akhavan 2011) routes have been
explored in recent times. However, each of the afore-mentioned processes has major
drawbacks, for example, electrochemical methods fail to remove inherent defects
present in GO as well as lead to the formation of stable ether or carbonyl groups which
are tough to eliminate (Aunkor et al. 2016). Moreover, the thermal and photocatalytic
pathways are associated with complex multistep mode of operation and requirement
of specially designed materials that can withstand uninterrupted ultraviolet radiation,
respectively. These limitations coupled with the relatively fast and flexible nature of
the chemical mediated reduction of graphene, researchers have widely regarded it as
the easiest and most prudent route for the production of graphene with interesting
morphological features (Low et al. 2015). Since the reduction of GO by chemical
methods (hydrazine, NaBH 4 , hydroquinone, etc.) involves the problems associated
with the production and disposal of toxic waste streams, researchers have turned
their attention toward the conversion of GO to RGO by employing environmentally
benign reducing agents. However, the reduction of GO via non-toxic routes involves
reducing agents that are expensive, scarce, and prone to degradation during storage
(Aunkor et al. 2016; Low et al. 2015). In the span of the last few years research efforts
have been directed toward the identification and effectiveness of such green sources
that can successfully reduce GO without interfering with the inherent structural
properties. Previous works have shown the reduction of GO can be carried out using
coconut water, clove extract, tea polyphenol, amino acids, pomegranate juice, and
spinach extract as highlighted in some excellent review papers (Aunkor et al. 2016;
De Silva et al. 2017). In this work, we have used the extract of apple (Maluspumila)
to carry out the reduction of GO in aqueous medium. It is expected that the malic acid
present in the apple extract will facilitate the reduction of GO as well as preventing
the agglomeration of graphene into the pristine graphitic structure. The advantage of
this process compared to other chemical reducing agents is the easy availability of
the precursor involved and overall environmental consequences.
S. Mitra et al.
application in a variety of different branches such as lithium-ion batteries (Wu et al.
2010), supercapacitors (Bose et al. 2017a, b), electronic devices (Guo et al. 2010),
tribology (Eswaraiah et al. 2011), and fillers for nanocomposites (Bose et al. 2017a,
b, 2018, 2019). Therefore, huge requisition for graphene and its peaking cost of largescale production demands substantial reduction in the production cost associated with
it. Compared to the preparation of graphene from graphite using various mechanical
routes (Dikin et al. 2007), the reduction of graphene oxide (GO) offers a promising
alternative for the mass production of graphene. Properties of the reduced graphene
oxide (RGO) are affected by the characteristics of the GO used in the synthesis step
(Subrahmanyam et al. 2009). The reduction of GO via electrochemical (Raj and John
2013), thermal (Liu et al. 2013), and photocatalytic (Akhavan 2011) routes have been
explored in recent times. However, each of the afore-mentioned processes has major
drawbacks, for example, electrochemical methods fail to remove inherent defects
present in GO as well as lead to the formation of stable ether or carbonyl groups which
are tough to eliminate (Aunkor et al. 2016). Moreover, the thermal and photocatalytic
pathways are associated with complex multistep mode of operation and requirement
of specially designed materials that can withstand uninterrupted ultraviolet radiation,
respectively. These limitations coupled with the relatively fast and flexible nature of
the chemical mediated reduction of graphene, researchers have widely regarded it as
the easiest and most prudent route for the production of graphene with interesting
morphological features (Low et al. 2015). Since the reduction of GO by chemical
methods (hydrazine, NaBH 4 , hydroquinone, etc.) involves the problems associated
with the production and disposal of toxic waste streams, researchers have turned
their attention toward the conversion of GO to RGO by employing environmentally
benign reducing agents. However, the reduction of GO via non-toxic routes involves
reducing agents that are expensive, scarce, and prone to degradation during storage
(Aunkor et al. 2016; Low et al. 2015). In the span of the last few years research efforts
have been directed toward the identification and effectiveness of such green sources
that can successfully reduce GO without interfering with the inherent structural
properties. Previous works have shown the reduction of GO can be carried out using
coconut water, clove extract, tea polyphenol, amino acids, pomegranate juice, and
spinach extract as highlighted in some excellent review papers (Aunkor et al. 2016;
De Silva et al. 2017). In this work, we have used the extract of apple (Maluspumila)
to carry out the reduction of GO in aqueous medium. It is expected that the malic acid
present in the apple extract will facilitate the reduction of GO as well as preventing
the agglomeration of graphene into the pristine graphitic structure. The advantage of
this process compared to other chemical reducing agents is the easy availability of
the precursor involved and overall environmental consequences.